In 1603 a London publisher called Edward Blount, the man who later commissioned the First Folio of Shakespeare’s collected plays, brought out a handsome volume with a lengthy title: “The Essayes or Morall, Politike and Millitarie Discourses of Lord Michaell de Montaigne, Knight of the noble Order of St Michaell, and one of the Gentlemen in Ordinary of the French king, Henry the third his Chamber . . . First written by him in French. And now done into English by John Florio.” A diverse collection of meditations on the art of being human and living well, learned yet light, sinuous and digressive, above all witty and humane, it was this book, perhaps above all others, that shaped the mind of Shakespeare in the second half of his career.

Shakespeare may well have known the translator John Florio, who was not only famous for having produced the standard English-Italian dictionary, but also happened to have been tutor to Henry Wriothesley, 3rd Earl of Southampton, at exactly the time when Shakespeare was angling for the glamorous young lord’s patronage. Personal acquaintance is a probability; knowledge of Florio’s Montaigne is a certainty.

How do we know that? The answer is to be found in Shakespeare’s last solo-authored play, The Tempest, a work sometimes seen as a self-conscious meditation on his own art. Soon after the shipwreck that begins the play, the good old counsellor Gonzalo says what he would do if he had the power to establish a colony, a “plantation”, on the island. He would create a utopian community, in which property would be held in common, nobody would have to work, and there would be no crime but a great deal of free love. His oration is an exact transcription, with some amplification, of a passage in Montaigne’s essay “Of the Cannibals”, as translated by Florio. Seen in this light, it is no coincidence that Shakespeare’s quasi-indigenous “savage” is, anagrammatically, called Caliban.

Montaigne, as translated by Florio, reports that among the “cannibals” of the new world, “The very words that import lying, falsehood, treason, dissimulations, covetousness, envie, detraction, and pardon, were never heard of . . .” He claims that he got this information from a traveller who had visited South America. He idealises indigenous peoples in order to criticise his own allegedly more civilised country – a France that had torn itself apart in religiously motivated civil war. The cannibals only eat the flesh of dead human beings, Montaigne notes wryly, whereas in super-sophisticated Europe we burn our religious enemies alive at the stake. We are the real savages.

Ludicrously, the critic Harold Bloom once proposed that Shakespeare invented our idea of what it is to be human. Far more plausibly, one could argue that Montaigne and Shakespeare between them effected a seismic shift in our sense of the autonomy of the individual, the sense of the self, and the western tradition’s acknowledgement of cultural difference and relativity of values.

In King Lear, which Shakespeare wrote soon after reading the Florio translation, the Earl of Gloucester blames all the ills of the world on the stars: “These late eclipses in the sun and moon portend no good to us.” His illegitimate son Edmund disputes this: “. . . an admirable evasion of whoremaster man, to lay his goatish disposition to the charge of a star!” Edmund argues that things often regarded as the “natural order” are in fact “custom”. For him, primogeniture and the stigmatisation of bastardy would come into this category. The position articulated here is close to that of Montaigne in the closing section of his longest essay, a critique of the theory of natural religion entitled “An Apology of Raymond Sebond”: any custom abhorred or outlawed by one nation is sure to be praised or practised by another. Montaigne was among the first to argue that many of the things generally said to be determined by nature or fate or God are in fact shaped by us, by society and tradition.

It was also in Florio’s translation of Montaigne’s “Apology of Raymond Sebond” that Shakespeare encountered a vision of “man all naked”: “I find we have had much more reason to hide and cover our nakedness, than any creature else. We may be excused for borrowing those which nature had therein favoured more than us, with their beauties to adorn us, and under their spoils of wool, of hair, of feathers, and of silk to shroud us.” The idea stuck, and was given to Lear: “Is man no more than this? Consider him well. Thou ow’st the worm no silk, the beast no hide, the sheep no wool, the cat no perfume. Ha! here’s three on ’s are sophisticated; thou art the thing itself; unaccommodated man is no more but such a poor, bare, forked animal as thou art.”

Montaigne’s point is that it is arrogant and illogical to suppose that human creatures are “naturally” superior to other animals or chosen by God as the supreme beings, since in our natural state of nakedness our bodies have defects, vulnerability and “manifold imperfections” in comparison to those of animals, adorned as they are with wool, hair or feathers that we borrow in order to clothe ourselves. King Lear, on the heath in the storm, sees “Poor Tom” in a state of primary nakedness, without the silk of the worm, the hide of the beast or the wool of the sheep (let alone the perfume that is taken from the cat) and starts to take off his clothes so that he, too, can return to the state of nature.

But if man is no more than an animal and if you have nothing save custom, no divinely sanctioned hierarchy, then where does your value system come from? Shakespeare’s Edmund commits himself to “nature” as a principle of survival and self-seeking. In this, he offers a foretaste of Hobbes’s Leviathan, a doctrine of raw competition. Montaigne argued instead for Christian love and humility. At the end of the Sebond essay, he suggests that all we can do is fall back on God: “Whatsoever we attempt without his assistance, whatever we see without the lamp of his grace, is but vanity and folly.” Raymond Sebond had argued that you could infer God from the order of created nature and from human reason. The “apology” in Montaigne’s title is ironically meant: the essay comprehensively refutes Sebond’s natural religion and says that what you need instead is blind, irrational faith. For all his scepticism, Montaigne retained a deep and abiding personal faith, which is one of the few things that sets him apart from Shakespeare (at least as far as the work is concerned – we will never know what faith Shakespeare did or did not hold in his heart).

Montaigne’s work is a perpetual critique of abstract wisdom in the name of experience. Shakespeare engages in a similar critique throughout his career. He always finds theory wanting in the face of action. He is more interested in how people perform than in what they profess. He was, after all, a performer. His reading of Montaigne in Florio’s translation some time before the writing of Lear gave him a philosophically articulated basis for his own long-standing practice.

“What do I know?” Montaigne asks. I know experience, he replies to himself in his final essay. In his art of self-interrogation, he is Hamlet incarnate, his literary form – an essai means a trial, an assay, a self-testing – an anticipation of the art of the soliloquy. Scholars debate whether or not Shakespeare saw Florio’s translation in manuscript before it was published in 1603. The balance of evidence suggests that he probably did not, but rather that his mind and Montaigne’s worked in such similar ways that the character of Hamlet, created before 1600, seems like a reader of Montaigne even though he could not have been.

Imagine that Hamlet could have read Montaigne. He would have found a meditation on the pros and cons of suicide in an essay called “Of a custom of the Isle of Cea”, but he would most characteristically have turned to the essay in Montaigne’s first volume, strongly influenced by Cicero, called “That to philosophise is to learn how to die”. As a university-educated reader, Hamlet would have been trained to copy the pithiest wisdom from his reading into his commonplace book, known as his “tables”. We can readily imagine the princely student of Wittenberg copying out a sentence such as the following: “Cicero saith, that to Philosophise is no other thing than for a man to prepare himself to death: which is the reason that study and contemplation doth in some sort withdraw our soul from us and severally employ it from our body, which is a kind of apprentisage and resemblance of death; or else it is, that all the wisdom and discourse of the world doth in the end resolve upon this point, to teach us not to fear to die.”

Hamlet would have relished the double sense there. The action of study and contemplation is a little rehearsal for death, in that it involves a withdrawal from the bustle of life. At the same time, the ultimate content of philosophy is the knowledge that we are all going to die, and that we should accordingly, as the Duke puts it in Measure for Measure, “Be absolute for death.”

The Duke’s oration to the condemned Claudio offers a neo-Stoical mix of classical resignation and Christian contempt for worldliness. Montaigne and Hamlet have a subtly different emphasis. They seek to cultivate contempt not for the world, but for death. They teach themselves to be ready, but not to be afraid. A fool, says Montaigne, deals with fear of death by not thinking about it. A wise man simultaneously thinks about it all the time and gets on with his life: “Now of all the benefits of virtue, the contempt of death is the chiefest, a mean that furnisheth our life with an easeful tranquillity and gives us a pure and amiable taste of it . . . let death seize upon me whilst I am setting my cabbages, careless of her dart, but more of my unperfect garden.” We do not know whether Shakespeare grew cabbages in his garden at New Place, but it is a reasonable bet that he would have shared Montaigne’s hope of ending his life in some such way.

Although Florio’s translation appeared as a single volume, Montaigne’s essays were published in three, over many years. Such is their variety and intellectual flexibility that it is hard to generalise about them – they are indeed written against generalisation. But scholars have discerned a broad progression from a predominance of neo-Roman Stoicism in the first book, to rigorous scepticism in the second, to the third’s embrace of pleasure in the moment and acceptance of contingency, mortality and the needs of the body. The remarkable penultimate essay, innocuously entitled “Upon some verses in Virgil”, is about sex and how we shouldn’t be ashamed of it and, in particular, about how sexual desire remains with us even when we are old.

The philosophical tradition that fits with the tenor of Montaigne’s final essays is that of Epicureanism. In an intellectual biography of Shakespeare called Soul of the Age (2008), I suggested that if we were to pin any philosophical label on the myriad-minded Bard, “Shakespeare the Epicurean” would be about as good as we could get. I noted in particular the very Epicurean sense of acceptance in what were probably the last words he wrote for the theatre, Theseus’s closing speech in The Two NobleKinsmen:

. . . O you heavenly charmers,
What things you make of us! For what we lack
We laugh, for what we have are sorry, still
Are children in some kind. Let us be thankful
For that which is, and with you leave dispute
That are above our question.

Reviewing the book, Stephen Greenblatt, the leading Shakespearean in the United States, was somewhat sceptical of this line of argument. But he has since written a wonderful book on the significance for the Renaissance of that profound philosophical Epicurean, Lucretius; and it is gratifying that Greenblatt, in his exemplary introduction to this exemplary selection of the essays of Montaigne that most influenced Shakespeare, quotes the same passage to make a similar link with Montaigne’s third book and the tradition of pragmatic Epicureanism. I can only wish that his bibliography had got the title of my book right.